October 3, 2023
Speaker: Ralph Schoenrich (University College London)
Contact Information: r.schoenrich@ucl.ac.uk
Title: Spinning into darkness: the slowing bar and Galactic structure
Abstract:
In the inner Milky Way stars trek together in a bar-shaped, rotating overdensity: the central bar, which dominates the inner disc out half-way to the Sun. The rotation velocity/pattern speed of this bar has been intensely debated. The best insight into the bar's motion are gained from its resonant effects on the Milky Way disc: Similar to Jupiter holding in resonant motion Solar System asteroids like Greeks and Trojans, some stars near the Sun are locked in resonant motion, e.g. in corotation resonance circling the Lagrange points on the bar's minor axis. When the bar slows, these resonances move outwards through the Galaxy dragging bound stars along. Along their path they can pick up new stars. The corotation resonance is enhanced by this process, explaining the high contrast of the observed Hercules stream. My group has used this to measure for the first time the slowing of the bar's rotation. We have also resolved long-term issues with bar pattern speed measurements. This also promises new insights into the Milky Way's history. Most importantly, the bar's slowing can only be explained with angular momentum loss to the Milky Way's dark matter halo, thereby proving its inertial mass.
Visitor's room: 103A
Visit Schedule:
Wednesday (October 4, 2023):
9:30 a.m.:
10:00 a.m.: Jeremy Goodman
10:30 a.m.: Astrocoffee (Grand Central)
11:00 a.m.: Jo Dunkley (103A)
11:30 a.m.:
12:00 p.m.: Wunch
12:30 p.m.: Wunch
1:00 p.m.: Ivanna Escala (103A)
1:30 p.m.:
2:00 p.m.:
2:30 p.m.: Philipp Kempski
3:00 p.m.: Shaunak Modak (103A)
3:30 p.m.:
4:00 p.m.:
5:00 p.m.: Robert Lupton (25D -- basement near loading dock)
Thursday (October 5, 2023):
9:30 a.m.:
10:00 a.m.:
10:30 a.m.: Astrocoffee
11:00 a.m.:
Dinner Sign-up - add your name here:
Wednesday (October 4, 2023)
Ralph Schoenrich
Faculty Host: Gaspar Bakos
Postdoc Host: Ivanna Escala
Amir Siraj
Shaunak Modak
Miguel Montalvo
Jeff Shen
Robert Lupton
STUDENTS HAVE PRIORITY.
PLEASE NO MORE THAN 8 PEOPLE (it is more difficult to properly interact with the speaker in larger groups).